GRB 200228A

The Fermi GBM team reports the detection of a likely LONG GRB

At 06:58:33 UT on 28 Feb 2020, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 200228A (trigger 604565918.806272 / 200228291).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 328.0, Dec = -46.5 (J2000 degrees, equivalent to J2000 21h 52m, -46d 30'), with a statistical uncertainty of 1.5 degrees.

The angle from the Fermi LAT boresight is 33.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200228291/quicklook/glg_skymap_all_bn200228291.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200228291/quicklook/glg_healpix_all_bn200228291.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200228291/quicklook/glg_lc_medres34_bn200228291.gif

F. Kunzweiler, B. Biltzinger, F. Berlato, J. Burgess & J. Greiner (all MPE Garching) report:

The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
604565918 at 06:58:33 on 28 Feb. 2020 were automatically fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).

The best-fit position (1 sigma statistical errors) is:
RA(2000.0) = 332.9+/-0.9 deg
Decl.(2000.0) = -39.9+/-1.0 deg
We estimate an additional systematic error of 1 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB200228291/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB200228291/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB200228291/json

Aaron Tohuvavohu (U Toronto), James DeLaunay (PSU), and Jamie Kennea
(PSU) report:

Swift/BAT did not trigger on GRB 200228A, likely due to a slew.

The Fermi/GBM Flight-Position notice, distributed at T0+23 seconds,
from the Fermi/GBM detected GRB 200228A (GCN. 27247) triggered the
Swift Mission Operations Center operated Gamma-ray Urgent Archiver for
Novel Opportunities (GUANO; Tohuvavohu et al. 2020, in prep).

The GUANO is a fully autonomous, extremely low latency, spacecraft
commanding pipeline designed for targeted recovery of BAT event mode
data around the times of compelling astrophysical events to enable
more sensitive GRB searches.

Upon trigger by the Fermi notice, GUANO sent a command to the Swift
Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data
from [-50,+150] seconds around the time of GRB 200228A.

All the requested event mode data was delivered to the ground.

In a ground analysis of the data, using the normal BAT imaging
technique, we detect GRB 200228A with a SNR of 40.

The BAT ground-calculated position is
RA, Dec = 333.8928, -42.9443 deg which is
   RA(J2000)  = 333d 53��� 34.08���
   Dec(J2000) =  -42d 56' 39.48"
with an uncertainty of 3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 34%.

This arcminute location is consistent with the localization region
distributed by the Fermi/GBM team (GCN. 27247).

No XRT or UVOT follow-up will take place due to the source���s proximity
to the sun (0.5 hours).
We encourage follow-up from instruments capable of observing near the sun.

E. Bissaldi (Politecnico and INFN Bari)
reports on behalf of the Fermi GBM Team:


"At 06:58:33.81 UT on 28 February 2020, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 200228A (trigger 604565918 / 200228291), as reported
by the Fermi GBM Final Real-time Localization (GCN 27247
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 ).
The GBM localization is consistent with the Swift GUANO localization
(Tohuvavohu et al. 2020, GCN 27259
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 ).

The angle from the Fermi LAT boresight at the GBM trigger time is 33 degrees.

The GBM light curve consists of a single bright peak
with a duration (T90) of about 4 s (50-300 keV).
The time-averaged spectrum from T0 to T0+4 s is
adequately fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.61 +/- 0.04 and
the cutoff energy, parameterized as Epeak, is 165 +/- 5 keV.

The event fluence (10-1000 keV) in this time interval is
(6.44 +/- 0.13)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1.0 s in the 10-1000 keV band
is 20.4 +/- 0.4 ph/s/cm^2.

A Band function fits the spectrum equally well
with Epeak= 153 +/- 7 keV, alpha = -0.54 +/- 0.05 and
beta = -2.85 +/- 0.23.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html

For Fermi GBM data and info, please visit the official Fermi GBM Support Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"

S. Gupta, V. Sharma and D. Bhattacharya (IUCAA), V. Bhalerao (IIT-B), A. R. Rao (TIFR) and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:

Analysis of AstroSat CZTI data showed the detection of the long GRB 200228A, which was also detected by Fermi GBM Final Real-time Localization (GCN #27247
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 ), BALROG (Kunzweiler F. et al., GCN #27248
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 ) and Swift/BAT (Tohuvavohu A. et al., GRB #27259).

The source was clearly detected in the 40-200 keV energy range. The light curve showed a single peak of emission peaking at 2020-02-28 06:58:33.01 UT. The measured peak count rate associated with the burst is 537 +/- 33.1 cts/s above the background in the combined data of four quadrants, with a total of 1496 +/- 9.8 cts. The local mean background count rate was 551 +/- 1.4 cts/s. Using cumulative rates, we measure a T90 of 4.8 +/- 0.02 s.

It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range.

CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.